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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        table,tr,td,th{
            border: 1px solid #dddddd;
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    <div>
        <table summary="">
            <tr>
                <th>班级</th>
                <th>学生数</th>
                <th>平均成绩</th> 
            </tr>
             <tr>
                <td>一班</td>
                <td>30</td>
                <td>89</td>
            </tr>
            <tr>
                <td>二班</td>
                <td>35</td>
                <td>85</td>
            </tr>
            <tr>
                <td>三班</td>
                <td>32</td>
                <td>80</td>
            </tr>
        </table>
        <table summary="">
            <tr>
                <th>班级</th>
                <td>一班</td>
                <td>二班</td>
                <td>三班</td>
            </tr>
             <tr>
                <th>学生数</th>
                <td>30</td>
                <td>35</td>
                <td>32</td>
            </tr>
            <tr>
                <th>平均成绩</th>
                <td>89</td>
                <td>85</td>
                <td>80</td>
            </tr>
        </table>
    </div>
</body>
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